A couple, yes.
Despite what you learned in Sunday school, your first best option is to lie. When asked for an e-mail address for no apparent good reason, feel free to enter and smack the Return key. With luck, the Web site will take this as the goods and let you get on with your business.
Regrettably, this technique doesn't work as well as it once did. Increasingly, you're asked to submit an e-mail address and then the asking body sends you a link to whatever you've requested via e-mail. If the address you submit is no good, you don't receive the message, and you can't get the thing you were after.
That doesn't mean, however, that you must offer your primary e-mail address. I've created a couple of free Google and Yahoo addresses for exactly this purpose. When asked for an e-mail address that I know will result in an activation message, I plunk in one of these addresses. I then check that account for the activation e-mail and then ignore the account until I next need it. (Meaning I don't include it in a schedule that automatically checks my e-mail.)
If you want to get very fine with this, you can create a new account for each place you visit. For example, if you must submit your e-mail address to Company X, create a new Google account for . Should you receive spam at this address, you have a reasonable idea of who's responsible. At that point you can complain or swear off that company in the future.
If you have a MobileMe account you can create up to five alias addresses. Messages sent to these aliases are forwarded to your primary MobileMe address. So, for example, when dealing with the famed Company X, create an alias for . After you've received Company X's activation e-mail, delete the alias. Any future messages sent to this account won't go through as it's now a dead address.